Money is not paid for overheard rumours in pubs, the police said

The Met paid out �2,220,574 in rewards for information about criminals operating in London and in other areas.

Another �134,961 was spent on "informant related expenditure", thought to include accommodation, travel and food for police handlers.

Senior officers have said that such knowledge is crucial in fighting organised crime and terror threats.

London's police spent �2,225,893 on informants in 2005-6 and �143,606 more on related costs.

Most of our informants are doing this purely for money and they are involved in the criminal lifestyle and their lives are often at risk Assistant Commissioner Steve House

But the Met, like other police forces across England and Wales, has refused to give details of the total amount it spends on informants, even after a Freedom of Information Act request.

Assistant Commissioner Steve House said informants were a vital source of intelligence, but said the idea of people being paid small amounts for rumours overheard in pubs was not accurate.

Mr House said in a public meeting last month that certain details could not be divulged in order to protect informants.

Secrecy criticised

He said: "Most of our informants are doing this purely for money and they are involved in the criminal lifestyle and their lives are often at risk.

"The lack of transparency is to a certain extent deliberate. Informants, or as they are now called, Covert Human Intelligence Sources, are covert assets.

"It is not good sense to tell too much about any covert assets. We do not give too much detail."

Critics say some of the procedures could be abused because cash changes hands under a cloak of secrecy.

Metropolitan Police Authority member Jenny Jones said she will discuss the amount paid with Sir Ian Blair at the next meeting of the oversight group.

Criticising the secrecy, she said: "This is a classic example of information the police could easily have given us."